Undetermined · NTSB WPR12FA154
CESSNA T182 — Ludlow, CA
| Date | April 6, 2012 |
| Location | Ludlow, CA |
| Aircraft | CESSNA T182 |
| Purpose of flight | Personal |
| Conditions | Night/Bright · Visual Meteorological Cond |
| Phase / occurrence | Enroute Altitude deviation |
| Pilot age | 63 |
| Pilot total time | 728 hrs · Building experience |
| Time in type | 464 hrs |
| Fatalities | 1 |
Probable cause
NTSB findings
- Personnel issues-Task performance-Use of equip/info-Aircraft control-Pilot - C
- Personnel issues-Physical-Impairment/incapacitation-Hypoxia/anoxia-Pilot - C
- Personnel issues-Action/decision-Info processing/decision-Decision making/judgment-Pilot - F
What happened
After departing on a cross-country flight in night visual meteorological conditions, the pilot requested flight following from air traffic control. According to radar data, about 11 minutes after takeoff, the airplane leveled off at 14,800 feet mean sea level (msl). About 30 minutes later, when the airplane was still about 150 miles from its destination, air traffic controllers observed the airplane beginning to descend. When air traffic controllers subsequently questioned the pilot as to his intensions, the pilot’s responses were garbled and unintelligible. Radar data indicated that the airplane continued a meandering descent until it descended through about 11,000 feet msl and radar contact was lost. The airplane impacted terrain in a right-wing-low attitude, and the debris field extended about 830 feet.
Postaccident examination revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation. The investigation revealed that the pilot had flown for about 40 minutes at altitudes exceeding 12,500 feet msl, with much of that time spent at 14,600 feet msl. At these altitudes, without the use of supplemental oxygen, the pilot would have become hypoxic (insufficient brain oxygen). Although the pilot’s wife indicated that he typically used supplemental oxygen when operating above 11,000 feet msl and supplemental oxygen was available to the pilot during the flight, postaccident investigation indicated that no cockpit oxygen ports were in use when the accident occurred.
The degree of hypoxia experienced by the pilot would have severely degraded his performance. Both the garbled transmissions to air traffic controllers and the airplane’s meandering flight path are consistent with the pilot experiencing symptomatic hypoxia. As the airplane descended during the last few minutes of the flight, the pilot’s oxygen saturation would have slowly improved; however, the rate of descent was likely too rapid to allow the pilot to recover his vision and judgment in time to prevent the accident.